This invention generally relates to an elastomeric barrier film as an inner liner, and to pneumatic rubber substrates and rubber tires having such elastomeric barrier film as the inner liner. More particularly, this invention relates to formulated chlorinated polyethylene film as an inner liner, and to the pneumatic rubber substrates and the rubber tires incorporating such a film as an inner liner.
Chlorinated polyethylene, particularly chlorinated polyethylene containing from about 30 to about 50 weight percent chlorine is a useful elastomeric material, and upon being sufficiently cured becomes a rubbery material having improved physical properties such as heat resistance, superior mechanical properties and the like.
It in known that cured or uncured and curable chlorinated polyethylenes (CPE) are useful as rubber materials because of improved properties, in jacketing electrical wires and in hoses because of their excellent heat and oil resistance. However, the utility of chlorinated polyethylenes as inner liners for tires as providing superior air impermeability, heat resistance and other improved mechanical properties has heretofore not yet been discovered. It was typically expected that CPE would not have adequate air impermeability or heat resistance for such an application.
Pneumatic tires generally have a rubbery elastomeric inner liner which forms the inner surface of the tire. This inner liner is designed to retard or minimize the permeation of air used to inflate the tire, and aid in maintaining the air pressure of the tire. Typically, the inner liner is composed of rubbers which are relatively impermeable to air. Such rubbers include butyl and halobutyl rubbers.
The inner liners based on rubber compositions represent the most expensive component in the tire construction. They also add weight to the tire because relatively thick inner liner coatings are generally necessary to obtain the desired degree of air impermeability. Typically, a butyl rubber liner must be 60 mils thick to provide the necessary air barrier properties.
The inner liners based on blends of butyl rubber with a natural rubber or reclaimed butyl rubber or both experience difficulty due to diffusion of gases, particularly air through the liner.
U.S. Pat. No. 4,616,687 discloses vulcanizing compositions containing from about 80% to 99% rubber material selected from butyl rubber, and halogenated butyl rubber; and 20% to 1% of a chlorinated hydrocarbon polymer having a chlorine content of from about 30% to 70% by weight of chlorine. The chlorinated hydrocarbon of this composition is selected from the group consisting of chlorinated polyisoprene having chlorine content from about 63 to 66% by weight, and chlorinated polyolefin having a chlorine content from about 30 to about 70% chlorine. However, this composition is composed predominantly of rubber material which is preferably a halobutyl rubber, and the teaching does not address the disadvantages such as cost, weight and the like associated with the use of a predominantly halobutyl rubber liner.
Accordingly, it is an object of present invention to provide an elastomeric film which can be used as an inner liner for rubber tires and which will be more economical and much lighter in weight than butyl or halobutyl rubbers or compositions containing predominantly halobutyl rubber, without losing desired properties such as air impermeability, heat resistance, mechanical properties and the like.
It is yet another object of the present invention to obtain a pneumatic rubber substrate or a tire which incorporates the elastomeric chlorinated polyethylene film of the invention, is light in weight and has the desired properties such as low temperature flexibility, ability to maintain air pressure, and heat resistance.